Nonwoven fabrics are used for a wide variety of applications from baby wipes and diapers to automobile covers and geotextiles. These applications call for materials having diverse properties and attributes. Some applications, for example, call for nonwovens which are highly wettable, i.e. quickly allow liquids to pass through them, e.g. diapers and feminine hygiene products and which are generally designed for short term use and disposability. Others require a high degree of repellence and photostability, e.g. outdoor fabrics like car covers, awnings and canopies for much longer term usage.
Since most nonwovens are made of polymers containing chromophores, they tend to be relatively reactive when exposed for long periods of time to sources of energy such as sunlight. This reactivity and subsequent oxidation of the fabric results in a serious deterioration of the tensile strength of the fabric. Therefore, one of the most difficult problems facing designers of nonwoven fabrics for outdoor use has been improving the retention of tensile strength upon exposure to sunlight, i.e.; the photostability of the fabric. A compounding difficulty has been that it is usually desired to color or pigment nonwoven fabrics for outdoor use as the original polymer color tends to be rather dull, and it has been found that most currently known pigments have a negative effect on the photostability of nonwoven fabrics. Further complicating the issue, many pigments contain colorants or other ingredients which are toxic and therefore not permitted. As a result, there is a small class of pigments useable in nonwoven fabric and they have a negative effect on the fabric life because of the deterioration of tensile strength they cause.
It is an object of this invention to provide a stabilization additive package for nonwoven webs which includes a pigment and which greatly improves the retention of tensile properties of the nonwoven web upon exposure to sunlight.
It is a further object of this invention to provide a nonwoven fabric having such a stabilization additive package.